Another vote for a shift in feeding times and putting him on a leash to go out that last time.
The fact he sometimes won’t leave the deck makes me think he may be worried about vision loss and/or may be creaky from age and not have enough motivation to move and work it out (esp if he had been laying down). That may mean posturing to potty is uncomfortable. Perhaps if you walk him a couple laps around the yard, that will encourage him to potty for you even if he can’t hear you asking.